The subject invention is directed to methods and apparatus for recording and monitoring of partial spaces and, more particularly, to methods and apparatus particularly adapted for determining seat occupancy in a motor vehicle and, based on the seat occupancy determination, activating or deactivating one or more accessory units of the motor vehicle such as, for example, seat belts and air bags.
One such switching device is taught in DE 38 02 159 A1, whereat the device releases or eliminates an activation of at least one accessory unit allocated in a motor vehicle to an adjustable seat, such as, for example, one or several passenger restraining elements of a passenger restraining system, a seat heating unit, etc. With respect to unoccupied seats of vehicles, it is possible, according to the above device to eliminate the activation of the accessory units. To that end, a vehicle seat position is recorded relative to the vehicle and the position of the seat elements relative to each other are similarly recorded. An ultrasound sensor including a transmitter and receiver is used to record the distance of a single seat location relative to the transducer. Measuring of distances are performed on the basis of an impulse-echo transit time method.
One disadvantage of the above-noted device, however, is that such switching devices do not distinguish between objects located or disposed upon the seat, such as, for example, a distinction between passengers and infant car seats containing a child disposed upon the seat. In addition, the actual distance measuring used to perform the evaluation is usually too imprecise and is generally dependent upon prior registration of seat distances or seat positions.